The Application Of Three-dimensional CT In Preoperation And Postoperation Of Developmental Dysplasia Of The Hip

Objective: Developmental dysplasia of the hip(DDH) is a common disease in the pediatric orthopaedics, acetabular dysplasia, nonconcentric hip-joint articulation and approximate femoral deformity are the main pathologic morphology abnormality. As the pathologic morphology changes of DDH are very complex, requiring the imaging technology to aid in diagnosis and treatment. After the mid-90s, three-dimensional CT(3DCT) imaging technique was widely used,it brought great convenience in the clinical use. This study was designed to evaluate the directive effect of three-dimensional computed tomography in the surgery of developmental dislocation of the hip and to provide a reasonable basis of the examination for clinic by analyzing 3DCT findings of the DDH .Methods: Collected clinical data of patients with DDH being treated in the Third Hospital of Hebei Medical University Pediatric Orthopedic from 2008.2 to 2009.6, According to the preoperative X-ray and the evaluation criteria of postoperative hip, unilateral DDH in 30 cases were detected, including 26 females and 4 males, ranging in age from 2 to 9 years , mean 4.2 years. The patients were treated with Salter or Chiari acetabuloplasty and femoral osteotomy. The German Siemens company's multi-slice spiral CT machine was performed in these patients of preoperation and postoperation over 6 months, The three-dimensional CT images were reconstructed by a workstation, the 3D images were watched and the relevant data was measured. Group: selected the 30 contralateral hips as a control group, the 30 affected hips as a preoperative group, the 30 postoperative hips as a postoperative group. 23 hips were treated by Salter innominate osteotomy, 7 hips were treated by Chiari pelvic osteotomy.Results: 1 Results of morphological observation of 3DCT, The normal acetabulum was round and the margin,socket fossa were smooth. The femoral head was spherical, surface smooth, homogeneous bone density, and good coverage of the femoral head. The femoral head of dislocation hip moved toward the outside, posterior and upward direction, different morphological changes, density inequality, uneven, slightly smaller and flat. Sometimes, the femoral head reached iliac wings and formed the pseudo-acetabulum with ilium. Three-dimensional CT images demonstrated the acetabulum became shallow and uneven and the acetabular lip became more irregular. The postoperative 3DCT images showed the femoral head was in the true acetabulum and contained well.2 The control group mean of the various parts of acetabular index(AI): anterior AI was 20.402°±3.173°, middle AI 22.714°±2.835°, posterior AI 20.793°±2.813°. The preoperative group mean of the various parts of AI: anterior AI was 38.155°±4.858°,middle AI 40.549°±4.509°, posterior AI 37.399°±4.745°.The postoperative group mean of the various parts of AI: anterior AI was 19.595°±2.652°,middle AI 21.637°±2.654°, posterior AI 21.133°±2.599°. The multiple comparison among the means showed: the control group compared with the postoperative group,there was no significant difference between two groups (P>0.05). The control group and the postoperative group compared with the preoperative group, there was significant difference (P<0.01).3 The mean of femoral neck anteversion(FNA) in the control group was 21.953°±5.641°. The variation in FNA of preoperative group, the greatest was 74.21°and the smallest was 35.17°, with average of 47.898°±9.802°, The mean of FNA in the postoperative group was 18.702°±5.116°.The multiple comparison among the means showed:there was significant difference between the control group and the preoperative group(P<0.01).The control group compared with the postoperative group,there was no significant difference between two groups(P=0.067>0.05).There was significant difference between the preoperative group and the postoperative group(P<0.01).4 The mean of femoral head coverage rate in the control group: anterior coverage rate was 0.848±0.026, middle coverage rate 0.819±0.023, posterior coverage rate 0.796±0.019. The mean of femoral head coverage rate in the post-operative group: anterior coverage rate was 0.868±0.052, middle coverage rate 0.836±0.039, posterior coverage rate 0.812±0.073. The control group compared with the postoperative group, there was no significant difference between two groups (P>0.05).Conclusion:1 The 3D reconstruction techniques can clear and intuitionistic reveal the change of structure and shape of femoral head and acetabulum.2 3DCT measurement methods of AI , FNA and femoral head coverage rate are accurate and effective.3 By 3DCT measurement, preoperative AI and FNA significantly higher than the control group, surgery should be corrected in order to maintain head acetabular concentric reduction.4 Three-dimensional femoral head coverage rate can reflect the true state of coverage of the femoral head.5 The 3DCT accurate measurement of various parameters has important directive to the preoperative treatment plan and postoperative objective assessment.6 3DCT widely used in clinical, it will lead to a new model to deal with DDH: stereoscopic observation, three dimentional measurement and individual design, precision orthotics and postoperative evaluation.